TTP 289A

THE PATH TO NET ZERO ENERGY (ZNE)

Robert Mondavi Institute (RMI) BUILDING

AnilShrestha

Claudia Llerandi

Tamara GuimarãesBucalo

Prof Kurt Kornbluth

TABLE OF CONTENT

EXECUTIVE SUMMARY

BACKGROUND

I. Problem description:

II. Clients

III. Objectives

IV. Literature Review

METHODOLOGY

I.Phase I – Interviews and data collection at the RMI laboratories

II.Phase II – Data collection and analysis for chilled water consumption

III.Phase III – Technology selection through an evaluative matrix

IV.Phase IV – Data collection for energy and economic savings

RESULTS AND DISCUSSION

I.Phase I – Defining the needs of all clients

II.Phase II – Energy and Mass Balance for Chilled Water at the RMI Building

III.Phase III – Technology Selection

IV.Phase IV – Economic Analysis

CONCLUSIONS AND RECOMMENDATIONS

REFERENCES

APPENDICES

Appendix A

Appendix B

Appendix C

Appendix D

EXECUTIVE SUMMARY

The purpose of the study was to recommend a suitable technology that could provide chilled water at the temperatures required for process loads at the Robert Mondavi Institute (RMI) building, in order to remove this load from the campus central heating and cooling plant (CHCP), which was forced to provide chilled water during the winter only to satisfy the needs from the RMI building. By providing a localized solution for chilled water consumption at the RMI building, the central heating and cooling plant (CHCP) will be able to operate at a higher efficiency, generating energy and economic savings.

In this study, the needs of RMI building were identified according to their specific purpose loads through a series of meetings and interviews with the lab managers working in the building. It was established that the RMI building currently requires water at 400F for the processes at the dairy lab and at the food pilot plant. The operation of the CHCP was also analyzed and possible economic savings were determined for a future scenario where the provided temperature for chilled water during the colder months would be of 500F, which would allow the CHCP plant to operate at a higher efficiency during the winter.

To satisfy the needs of all clients, the study was conducted and various technologies were analyzed according to the users priorities. An onsite electric chiller of 30 tons was recommended as the solution for providing better service at RMI building and saving energy at the CHCP. From the economic analysis in this study, the savings on energy will be $47.634 over the period of three years. The installation of an electric chiller is economically viable and will contribute to the overall energy savings of the University.

BACKGROUND

The 32,000-square-foot teaching and research complex, located within UC Davis Robert Mondavi Institute for Wine and Food Science, was officially opened on January 28, 2011. It is the one of the world’s most environmentally sophisticated and technologically advanced facilities for making wine, brewing beer, and processing foods and dairy products. It was financed entirely by private philanthropy — no state or federal funds were used. The campus received more than $20 million in private support to construct and equip the complex [1].

It is the first such building to receive LEED® (Leadership in Energy and Environmental Design) Platinum certification, the highest rating for environmental design and construction awarded by the U.S. Green Building Council [1].

The south wing of the complex is home to the August A. Busch III Brewing and Food Science Laboratory, which include the Anheuser-Busch InBev Brewery, the California Processing Tomato Industry Pilot Plant for processing and the Dairy Processing Laboratory. The complex's north wing houses the new Department of Viticulture and Enology Teaching and Research Winery [1].

The new winery, brewery and food-processing complex was designed to serve as a test bed for production processes and techniques that conserve water, energy and other vital resources. Its environmentally friendly features include onsite solar power generation and a large-capacity system for capturing, processing and conserving rainwater. The stored rainwater is used for landscaping and toilets. The building maximizes the use of natural light, outside air and temperatures during day and night to provide a confortable building temperature. The building also houses rooftop photovoltaic cells, which allows it to become positive net zero in terms of energy [1].

The air heating and cooling system for the building also utilizes steam and chilled water provided by the Central Heating and Cooling Plant (CHCP). The complex also requires water at different specified temperatures for different process loads, which are also currently maintained by using the chilled water and steam provided by the CHCP.

I. Problem description:

The CHCP provides chilled water at around 40°F and steam at around 350°F across the University steam and chilled water distribution system. During the Winter, when the air cooling systems of the buildings require very low energy, most of the chilled water pumped by the CHCP returns through the bypass valve which results in very small temperature difference between the supply and the return chilled water. As a result, the efficiency of chillers goes down and the cost of chilling the water goes up. Because of this, it is desirable to run the chillers at higher temperature (around 50°F) in winter so that the efficiency of chillers does not decrease.

The RMI building is the only building on the University campus that requires 40°F chilled water all year long because of its specialized process loads, which makes it mandatory for the CHCP to provide chilled water at this temperature even though it is more inefficient.

This conflicting nature of efficiency and necessity provides a challenge for energy savings and providing services to the University. The main purpose of this study was to determine whether a new onsite chilling system could provide better service at the RMI building and save the operating cost at the CHCP (Figure 1), and to supplement the current energy project underway, the student team will look into additional innovative technologies that could be applied to this building to achieve ZNE.

Figure 1. Proposed localized solution for the RMI building

II. Clients

  1. Central Heating and Cooling Plant (CHCP)

CHCP provides chilled water and steam for the building air-cooling systems at the UC Davis Campus and for the Health Science District (HSD). Currently, there are four large boilers and three chillers in the CHCP. All the chillers that were originally in the CHCP were substituted in the past 5 years with three high efficiency 2,500 tons electric chillers. There are two boilers that were constructed in 1967, which are very inefficient, old and have high maintenance costs. The third boiler was constructed in the 1990 decade and the fourth one was installed in 2009. The 10,350-ton chilled water plant was constructed sometime after 1999, and includes two electric chillers, two cooling towers, a thermal energy storage tank, and pipelines connecting the plant to the campus chilled water distribution system[2].

  1. Milk Processing Laboratory

The Milk Processing Lab is an invaluable resource to bring the bench-top research carried out at the FST Department to the translational stages in which all the important milk components can be safely isolated and tested for bioactive activity. It was designed to be highly flexible to allow the exploration of wide range of concepts, processes, packaging and products. All the instruments require minimum consumption of energy and water and can reach steady state quickly whileproducing little waste.The lab is currently equipped with a raw-milk cooling tank, cream separator, milk pasteurizer, milk homogenizer, ultraclean milk filler, a complete dairy analyzer (LactoScope) and a membrane separation system[3].

  1. Food Processing Pilot Plant

TheCalifornia Processing Tomato Industry Pilot Plant handles a broad spectrum of food products, including tomatoes, olives, peaches, prunes and has a flexible setup for teaching, research, outreach and contract work [4].

  1. Brewery

The Brewery is part of “The August A. Busch III Brewing and Food Science Laboratory”, which is 11,500 ft² and houses the brewery with a dry storage, millroom, records room and controlled-temperature room, as well as the food processing pilot plant and the milk processing laboratory mentioned above, classrooms and an analytical laboratory. Thebreweryis an authentic, reduced-scale facility, similar in size to smaller commercial brewing operations.

The winery, brewery, and food science laboratory building is the world’s first LEED Platinum-certified facility in their respective domains. LEED stands for Leadership in Energy and Environmental Design and has become the hallmark of sustainability in the architecture and construction world[5].

III. Objectives

Determine the requirements from each client regarding the temperatures and flows of chilled water in order to provide a better service that can satisfy the needs of them all.

Propose a localized solution that could provide chilled water at the required temperatures and flows to the RMI building that is efficient and generates energy savings.

Evaluate the economic feasibility for the proposed technology for chilled water generation on site.

IV. Literature Review

Technologies:

  1. Electric Chillers:

Electrical chillers use a motor driven compressor to chill the refrigerant.Generally, the refrigerants used are HCFCs, CFCs, HFC, etc. These refrigerants are greenhouse gases. CFC was phase out of production in January 1st, 1996 because of issues of ozone layer depletion [6].

Table 1: Comparison of refrigerant alternatives for electric chillers [6]

Criteria / HCFC-123 / HCFC-22 / HFC-134a / Ammonia
Ozone Depletion Potential / 0.016 / 0.05 / 0 / 0
Global Warming Potential (Relative to CO2) / 85 / 1,500 / 1,200 / 0
Ideal kW/ton / 0.46 / 0.50 / 0.52 / 0.48
Occupational Risk / Low / Low / Low / Low
Flammable / No / No / No / Yes

The electrical chillers can be classified according to the compressor used:

  1. Reciprocating Compressor Chiller:

The compressor in reciprocating compressor uses pistons in cylinders to increase refrigerant pressure. The number of piston-cylinder varies from 1 to 12,which unload in pairs as load decreases. These types of chillers dominate the market in small tonnage systems.[7]

  1. Centrifugal Compressor Chillers:

Centrifugal chillers are aerodynamic type chillers. They move fluid by converting kinetic energy to pressure energy. The compressor encases a refrigerant in a decreasing volume during the compression process. Centrifugal chillers are best suited for big chilling system because of the compressor variable volume load characteristics. They are generally quieter, require less maintenance and have less vibration than reciprocating compressors [7]. The main advantages of a centrifugal compressor are high flow rates capabilities and good efficiency characteristics [8].

  1. Screw Compressor Chillers:

Screw compressors are more compact than either centrifugal or reciprocating compressor. It consists of two matching helically grooved rotors, which turn, compressing the refrigerant gas as it passes from one end of the screws to the other. They are suited for lower temperature applications.[7]

  1. Scroll Compressor:

Scroll Compressor uses two spirals, one within the other to compress refrigerant. Often, one of the scrolls is fixed and the other orbits eccentrically without rotating, thereby trapping and compressing the pockets of fluids between the two spirals. The scroll compressors are very quiet and efficient. [9]

  1. Absorption Chiller:[10]

An absorption Chiller is a greentechnology that cools water using energy provided by a heat source. This technology differs from conventional chillers in the sense that it uses thermochemical absorption process to cool water instead of the mechanical process used in conventional chillers. In addition absorption chillers use water as refrigerant instead of chlorofluorocarbons.

The absorption chiller system uses water as refrigerant and lithium bromide as absorbent. Thus in the absorber the lithium bromide absorbent absorbs the water refrigerant and the solution of water and lithium bromide is formed. This solution is pumped to the generator to be heated. The water refrigerant gets vaporized and moves to the condenser where it is heated while lithium bromide flows back to the absorber where it further absorbs water coming from the evaporator.[10]

Absorption chillers are generally classified as direct or indirect fired and as single, double or triple effect. In directly fired units, the heat source can be gas or some other fuel that is burned in the unit. Indirect fired units make use of heat energy brought from somewhere else in the fluid.

  1. Single effect: In a single effect absorption chiller, the fluid transfers through four major components of the chiller-evaporator, absorber, generator and condenser once. The thermal efficiency of single effect chiller is low and they are frequently used to tap the waste heat energy.
  2. Double effect: In a double effect absorption chiller, the fluid transfers through two condensers and two generators to provide more refrigerant boil-off from the absorbent solution. It has higher efficiency than a single effect chiller.
  3. Triple effect: In a triple effect absorption chiller, the refrigerant vapor from the high and medium temperature generators is condensed and the heat is used to provide heat to the next lower temperature generator. The triple effect chillers are under development and they promise substantial performance improvements.

The advantages of absorption chillers are:

  • Elimination of use of CFC and HCFC refrigerants.
  • Quiet, vibration free operation.
  • Lower pressure systems with no large rotating components.
  • High reliability
  • Low maintenance

The limitations of absorption chillers are:

  • Cost is the primary constraint.
  • Low thermal efficiency.
  • Requires greater pump energy compared to electric chillers.
  • Requires larger cooling tower capacity.
  • Cooling up to 41-480F.

Figure 2: Working cycle of an absorption chiller [10]

  1. Adsorption Chiller:[13]

Adsorption chiller is a green technology, which cools water by using a heat source. The adsorption chiller uses water as refrigerant and permanent silica gel as an adsorbent. The silica gel has a very long life (around 30 years), which provides a long lifetime for these types of chillers. The evaporator section cools the chilled water by the refrigerant water being evaporated by adsorption of the silica gel in one of the two adsorption chambers. The adsorption chiller can produce chilled water temperatures of less than 38°F using hot water temperatures ranging from 194 to 122°F. The hot water regenerates the silica gel in the second of two adsorbent chambers. The water vapor released from the silica gel by hot water is then condensed in the condenser section.

Figure 3: Working cycle of an Adsorption chiller

The advantages of adsorption chillers are:

  • Tap water can be used as refrigerant,
  • Very long life time,
  • Do not need compressors,
  • No vibration or noise,
  • Chilled water up to 39°F can be delivered
  • High energy efficiency.
  • Reduction of carbon footprint.

The capacity of adsorption chillers is very large and not appropriate for small capacities since from the different quotations obtained for adsorption chillers for this project, the minimum capacity for a chiller found was of 110 ton.

  1. Water-to-water heat pump[14]

The water-to-water heat pump is a green technology, which can be used to cool and heat the water using the same equipment simultaneously. The R-410A is used as the refrigerant. The basic principle of a water source heat pump is the transfer of heat into water from the space during cooling or the transfer of heat from water in space during heating. It is designed to operate between 20°F to 90°F in cooling and 30°F to 120°F in heating for source and 60°F to 120°F in heating and from 30°F to 110°F in cooling for entering load temperatures.

METHODOLOGY

The overall approach of the project was divided in 4 phases: the first one consisted of defining the needs of the clients to better understand the problem at hand; the second one entailed estimating the capacity of chilled water that should be provided; the third phase involved the evaluation of the possible solutions and the selection of a technology that could provide the chilled water required; and the last phase consisted of an economic evaluation of the solution proposed.

I.Phase I – Interviews and data collection at the RMI laboratories

Phase I of the project was the one that involved the most data collection, thus, taking more time to be developed. It was intended to gather the most accurate data as possible, so meetings were scheduled with each of the clients to define what their requirements are and what they were really looking forward to with this project.

The following interviews were made to ensure that each of the clients would be interviewed at least once and several emails were exchanged to confirm their expectations, their needs and equipment specifications:

  • April 22nd, 2013 @ RMI Building: Joshua Morejohn (CHCP), Wyatt L. Kennedy and Tom (R&A Engineering Solutions) and Tamy.
  • April 25th, 2013 @ D-Lab: Joshua Morejohn (CHCP), Anil, Claudia and Tamy.
  • May 7th, 2013 @ Milk Processing Lab: Dr. Juliana Nobrega (MPL), Anil, Claudia and Tamy.
  • May 20th, 2013 @ Food Pilot Plant: Scott McCarthy (Food Pilot Plant), Anil, Claudia and Tamy.
  • May 20th, 2013 @ Brewery: Candace Wallin (Brewery Manager), Anil, Claudia and Tamy.

II.Phase II – Data collection and analysis for chilled water consumption

The following phase of the project was to estimate the total flow of chilled water necessary for all the process loads and the equipment in the labs. With an estimated flow rate for chilled water, different technologies could be evaluated for providing a local solution to the RMI building.